1. Field of the Invention
The present invention relates generally to an apparatus and method for measuring the circumferential spacing (pitch) between adjacent ones of a plurality of objects spaced about and rotatable with a rotor. The present invention has particular application to measurement of blade pitch in a turbine of the type having a plurality of blades disposed in at least one row about and rotatable with a rotor, and having a tenon disposed on the distal end of each blade for attachment to a shroud.
2. Description of the Prior Art
Presently, it is known to measure blade pitch manually with a modified vernier caliper. A blader uses the caliper to measure the chordal distance between the edges of adjacent tenons at points at the top of each tenon. The resulting measurement is known as measured pitch. The blader then applies a correction factor to the measured pitch to obtain the circumferential distance between the centers of adjacent tenons to obtain true pitch. The correction factor is manually computed from the mean tenon height (obtained from the blade drawing), mean shroud thickness (obtained from the shroud drawing) and a pitch measurement correction factor chart provided to the blader. The true pitch data is then manually entered onto another chart that is utilized for fabrication of the turbine shroud.
The above described method of measuring blade pitch does not provide accurate and consistent data. Problems arise from measurement inaccuracies and human error. Moreover, this method is time consuming, tedious and inefficient.
It is therefore desirable to provide an apparatus and method for the automated measurement of blade pitch that does not require the use of a caliper. It is also desirable to provide an apparatus for and method of measuring blade pitch that minimizes human intervention, and that is accurate, consistent and efficient to operate.